/**
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.lucene.search;

import java.io.IOException;

import org.apache.lucene.document.Document;
import org.apache.lucene.index.CorruptIndexException;

/**
 * Wrapper used by {@link HitIterator} to provide a lazily loaded hit from
 * {@link Hits}.
 * 
 * @author Jeremy Rayner
 */
public class Hit implements java.io.Serializable {

	private Document doc = null;

	private boolean resolved = false;

	private Hits hits = null;
	private int hitNumber;

	/**
	 * Constructed from {@link HitIterator}
	 * 
	 * @param hits
	 *            Hits returned from a search
	 * @param hitNumber
	 *            Hit index in Hits
	 */
	Hit(Hits hits, int hitNumber) {
		this.hits = hits;
		this.hitNumber = hitNumber;
	}

	/**
	 * Returns document for this hit.
	 * 
	 * @see Hits#doc(int)
	 * @throws CorruptIndexException
	 *             if the index is corrupt
	 * @throws IOException
	 *             if there is a low-level IO error
	 */
	public Document getDocument() throws CorruptIndexException, IOException {
		if (!resolved)
			fetchTheHit();
		return doc;
	}

	/**
	 * Returns score for this hit.
	 * 
	 * @see Hits#score(int)
	 */
	public float getScore() throws IOException {
		return hits.score(hitNumber);
	}

	/**
	 * Returns id for this hit.
	 * 
	 * @see Hits#id(int)
	 */
	public int getId() throws IOException {
		return hits.id(hitNumber);
	}

	private void fetchTheHit() throws CorruptIndexException, IOException {
		doc = hits.doc(hitNumber);
		resolved = true;
	}

	// provide some of the Document style interface (the simple stuff)

	/**
	 * Returns the boost factor for this hit on any field of the underlying
	 * document.
	 * 
	 * @see Document#getBoost()
	 * @throws CorruptIndexException
	 *             if the index is corrupt
	 * @throws IOException
	 *             if there is a low-level IO error
	 */
	public float getBoost() throws CorruptIndexException, IOException {
		return getDocument().getBoost();
	}

	/**
	 * Returns the string value of the field with the given name if any exist in
	 * this document, or null. If multiple fields exist with this name, this
	 * method returns the first value added. If only binary fields with this
	 * name exist, returns null.
	 * 
	 * @see Document#get(String)
	 * @throws CorruptIndexException
	 *             if the index is corrupt
	 * @throws IOException
	 *             if there is a low-level IO error
	 */
	public String get(String name) throws CorruptIndexException, IOException {
		return getDocument().get(name);
	}

	/**
	 * Prints the parameters to be used to discover the promised result.
	 */
	public String toString() {
		StringBuffer buffer = new StringBuffer();
		buffer.append("Hit<");
		buffer.append(hits.toString());
		buffer.append(" [");
		buffer.append(hitNumber);
		buffer.append("] ");
		if (resolved) {
			buffer.append("resolved");
		} else {
			buffer.append("unresolved");
		}
		buffer.append(">");
		return buffer.toString();
	}

}
